Under normal circumstances, the RA should be the main decision making body of the region. Proposals can be made to it to change or add laws, which it then discusses and votes on. Government officials are choosen from the RA, who are then tasked with carrying out the will of the region. The RA chooses the government officials via elections every 3 (? unless that has changed) months. The delegate of the region is also elected by the RA.
I've always imagined the RA being somewhat like a Roman senate, although I'm no expert on Roman politics, so I only have Spartacus to base that assumption on.
Political parties are allowed (or at least aren't banned) but have never really taken off in TNP. Unless you count "Old Guard" and "Crimson Whatnots" as parties...
The game mechanics of NS give all the power of the region to the Delegate, the nation with the most endorsements in the region. Liberation is just a case of gaining more endorsements than the current delegate.
Anyone else care to add some more?